In this photo taken on Tuesday, Oct. 21, 2014, a World War I bunker is situated on Aubers Ridge near Illies, France. Aubers Ridge offered German troops as of Oct. 1914 a strategic advantage by being located on the high ground near the River Lys. A century on, the four seasons bring constant changes

The Associated Press

In this photo taken on Tuesday, Oct. 21, 2014, a World War I bunker is situated on Aubers Ridge near Illies, France. Aubers Ridge offered German troops as of Oct. 1914 a strategic advantage by being located on the high ground near the River Lys. A century on, the four seasons bring constant changes to the scarred landscapes and ruins of the World War I battlefields in Belgium and northern France, yet many of the relics still exist, both above and below the surface. (AP Photo/Virginia Mayo)

In this photo taken on Tuesday, Oct. 21, 2014, a World War I bunker is situated on Aubers Ridge near Illies, France. Aubers Ridge offered German troops as of Oct. 1914 a strategic advantage by being located on the high ground near the River Lys. A century on, the four seasons bring constant changes to the scarred landscapes and ruins of the World War I battlefields in Belgium and northern France, yet many of the relics still exist, both above and below the surface. (AP Photo/Virginia Mayo) (The Associated Press)

In this photo taken on Tuesday, Oct. 21, 2014, a World War I bunker is situated on Aubers Ridge near Illies, France. Aubers Ridge offered German troops as of Oct. 1914 a strategic advantage by being located on the high ground near the River Lys. A century on, the four seasons bring constant changes to the scarred landscapes and ruins of the World War I battlefields in Belgium and northern France, yet many of the relics still exist, both above and below the surface. (AP Photo/Virginia Mayo)